The present invention relates to a composite charged particle beam apparatus for forming at a predetermined region of a sample surface by irradiating a focused ion beam while scanning over a predetermined region of the sample, and/or observing the sample and/or performing an elemental analysis of the sample surface by irradiating the sample with a focused ion beam and detecting secondary particles and/or an x ray generated in response to irradiation of the sample with an electron beam.
A composite charged particle beam has been realized which is capable of observing and analyzing a sample surface while scanning a focused ion beam or electron beam across a predetermined region of the sample in a sample chamber or irradiating it without scanning (switching, simultaneous irradiation, simultaneous non-irradiation are possible).
This is convenient because a position at which forming is being performed by a focused ion beam can be observed at the same time by a scanning electron microscope and analyzed by EDS.
However, because gallium is generally used as a liquid metal ion source for a focused ion beam, if there is a magnetic field in the path of the focused ion beam, gallium isotopes or clusters are mass-separated, resulting in deterioration in focused ion beam resolving power.
However, when a focused ion beam is to be used, if an excitation current of an objective lens of an electron beam lens barrel is rendered 0, the residual magnetism does not necessarily become 0. Accordingly, in a focused ion beam lens barrel in which a resolving power of approximately several nm is obtainable, even slight residual magnetism is problematic.
There is a residual magnetism countermeasure which provides a magnetic shield at a tip portion of a focused ion beam lens barrel to prevent it from being affected by leakage of a magnetic field from an objective lens of an electron beam lens barrel.
Meanwhile, among known electron beam lens barrels there is an objective lens of an in-lens or semi-in-lens type which is capable of obtaining a high resolving power that is large in magnetic field within a sample chamber. However, the above-mentioned magnetic shield cannot make the objective lens magnetic field asymmetrical. Accordingly, it has been impossible to adopt such an objective lens in a composite apparatus.
Another problem is that if the excitation current of the electron beam lens barrel is rendered 0 each time the focused ion beam lens barrel is used, there is a disadvantage in reproducibility in electron beam focusing when the electron beam lens barrel is to be used again.
An object of the present invention is to prevent resolving power deterioration by focused ion beam mass separation due to magnetic field leakage onto a focused ion beam path from ground magnetism, from an EDS detector or from an electron beam lens barrel and/or to improve the reproducibility of electron beam focusing by reducing the effect of objective lens hysteresis of the electron beam lens barrel.
In order to solve the above-stated problem, the present invention provides, in a composite charged particle beam apparatus having in a sample chamber one or more first charged particle beam generating systems such as focused ion beam lens barrels and one or more second charged particle beam generating systems such as electron beam lens barrels, an electromagnetic technique for neutralizing the residual magnetism of an objective lens of a charged particle beam generating system, particularly an electron beam lens barrel, and a function of storing a state of one of the charged particle beam generating systems, particularly an electron beam lens barrel, the stored state comprising, for example, an excitation current value of the objective lens of the electron beam lens barrel.
The objective lens residual magnetism of an electron beam lens barrel is neutralized when switching from the electron beam to a focused ion beam, whereby resolving power deterioration due to focused ion beam mass separation is prevented. When switching back to the electron beam, a memorized excitation current is supplied to the objective lens so that the residual magnetism is neutralized and electron beam focusing reproducibility can be improved.